Not applicable.
Golfers naturally pursue methods and tools to help them improve their golf game. For example, learning new personal strategies for a particular course or hole on a local range or gaining additional information of a course before first playing it can provide improved results. One of the informational tools currently available to a golfer is a printed scorecard or printed graphical course yardage guide. The scorecard provides a basic score keeping function and course specifications including approximate yardage per tee box. The graphical course guide typically provides a graphical representation of the course layout. It can also provide distances to some features for each hole.
The value of an informational tool to a golfer increases as the amount and accuracy of information the tool provides increases. There are several U.S. patents which relate to Global Positioning System (GPS) which provide accurate positional information to a golfer. Many of these patents are categorizable as relating to xe2x80x9ccart mounted inventions intended for course management communications and positional aids.xe2x80x9d These are under the control of the course manager and are, therefore, optimized for the manager""s use. Representative patents include:
U.S. Pat. No. 5,364,093; Golf Distance Measuring System and Method;
U.S. Pat. No. 5,524,081; Golf Information and Course Management System;
U.S. Pat. No. 5,685,786; Passive Golf Information System and Method;
U.S. Pat. No. 5,689,431; Golf Course Yardage and Information System; and
U.S. Pat. No. 5,740,077; Golf Round Data System.
These patents describe systems that are designed for purchase, installation, configuration and management by a golf course owner or manager. They fail to disclose a golfer owned and operated position information based system for use on any golf course by the golfer. Also, a disadvantage of course based systems is that golfers may feel continually monitored or bombarded by unwanted advertisements the course provided system creates, thus diminishing the quality of the golfing experience. Additionally, course based systems necessitate locating the GPS antenna on a self-propelled or pull-type cart which can be difficult or impossible to locate exactly where the golf ball is lying as is desirable for optimum performance.
Other systems, including various hand-held GPS based position information tools, lack many of the beneficial elements of the present invention as will be seen.
Various GPS related technologies are involved in the implementation and practice of prior systems and some embodiments of the present invention. By way of general background, a brief discussion of these technologies follows.
GPS/GLONASS
The Global Positioning System (GPS) is a satellite based navigation system operated and maintained by the U.S. Government. A constellation of 24 satellites provides worldwide, 24 hour, 3 dimensional (3-D) coverage. The determination of positions on a golf course utilizing GPS is well known in the art, and is explained in detail in U.S. Pat. No. 5,507,485, entitled GOLF COMPUTER AND GOLF REPLAY DEVICE which is incorporated herein by reference.
Since the GPS system was originally conceived as a military tool, the accuracy available to civilians may be degraded by the use of selective availability (SA). SA dithers the GPS signal to degrade its horizontal locational accuracy to within 100 meters 95% of the time. With SA off, as it is now, the accuracy of GPS based position information is within 12 meters, 95% of the time; and to within less than 6 meters, 50% of the time. The receipt and processing of GPS signals are now commonly accomplished using compact devices that are well known in the art. U.S. Pat. No. 5,271,034, entitled SYSTEM AND METHOD FOR RECEIVING AND DECODING GLOBAL POSITIONING SATELLITE SIGNALS, incorporated herein by reference, describes one such device. Most GPS receivers have from 5 to 12 channels, each channel receiving signals from a single satellite, for simultaneous line of site tracking of as many satellites as possible.
GLONASS is a Russian controlled satellite constellation providing substantially the same locational functionality as GPS. Other satellite constellations may be developed in the future that will provide adequate autonomous accuracies under 1 meter. There are numerous methods and systems of increasing the accuracy of satellite based position information, a short review of the most popular such methods follows.
Real Time Differential GPS
Differential Satellite Navigation Systems (DSNS), such as Differential GPS (dGPS) and Differential GLONASS (dGLONASS), utilize a strategy to improve the accuracy of GPS position determination information. It is based on the determination that the main sources of positional error in GPS are approximately equal over very large areas. DSNS use a comparison between the actual known position of a reference receiver and the position of the reference receiver calculated from the satellite system to determine what correction is necessary to reduce satellite system calculated position errors, known as psuedo-range errors, in the general vicinity of the reference receiver. For example, dGPS and DGLONASS systems use reference receivers at surveyed locations. These reference receivers are programed with their surveyed location information. They then receive signals from the satellites and calculate their position from that information. The reference receivers then establish the difference between their surveyed position and their calculated position (the pseudo range error) and broadcast the corrections that allow roving receivers in the region to correct their position calculations for these psuedo-range errors. This allows for the removal of the negative effects that SA, the ionosphere and troposphere and other error sources can have on positional accuracy. A common nonproprietary broadcast standard for this error-correcting information is RTCM SC-104 Version 2.
WAAS Differential
A Wide Area Augmentation System (WAAS) is being developed by the Federal Aviation Administration (FAA) to provide differential corrections on the same frequency as the GPS satellites. When operational, WAAS would eliminate the need for additional receivers currently employed for differential correction.
Marine Beacon Differential
Worldwide coastal and inland waterway navigation is aided through the use of radio beacons broadcasting differential corrections on the AM band in the frequency range of 283.5 kHz to 325 kHz. This broadcast signal has a range of a few hundred miles. As with GPS, receipt of the satellite signals is freexe2x80x94there is no periodic fee associated with the reception and use of this signal. This type of marine beacon radio signal encompasses the most populous golf courses in the world. Many world governments are currently expanding their radio beacon coverage areas and are planning new land-only locations. The Federal Government of the United States of America has committed, in addition to the United States Coast Guard (USCG) transmitters, to construct a National Differential GPS (NdGPS) system to provide redundant coverage of the contiguous United States. Further information can be found at the URL http://www.navcen.uscg.mil.
FM Subcarrier Differential
Differential Corrections can also be broadcast on a FM subcarrier with a range of about 30 to 50 kilometers from the transmitter. FM corrections are primarily proprietary broadcasts that have a periodic fee associated with their use.
Extended Satellite Differential (L Band)
In Extended Differential GPS systems, the differential reference stations are networked together to one or more master stations. The master station receives the error corrections from each reference station, then combines them into a differential format that will be valid over an extended range. The correction is then broadcast to users across the extended range, often via a satellite communications link. Satellite corrections are primarily proprietary broadcasts that have a periodic fee associated with their use.
Proprietary Local Differential
A private reference station situated near roving users (approximately 20 miles maximum range) can provide local differential corrections. These corrections can be broadcast, for example, on the 900 MHz or 2.4 or 3.6 GHz license-free frequencies. This is the preferred method of differential broadcast for cart-mounted and club owned or leased dGPS systems in the golf industry. The proprietary radio link typically provides two way digital communication between the club house and roving carts to facilitate differential correction, automatic vehicle location, advertisement transmission and course play monitoring by the course manager.
Internet Differential
Another method of supplying real time differential corrections to a roving GPS receiver on any golf course would be with a real time Radio Frequency (RF) Internet connection. Through this method, several surveyed locations such as cell phone towers would receive GPS signals, formulate correction values and make them available via the Internet. The roving unit requests the correction data, as needed, from the Internet server correction database.
Other errors in GPS receiver position determination which differential correction does not address, include the following:
Multipath Errors and Corrections
Direct signals are those received by the GPS receiver in a xe2x80x9cline of sightxe2x80x9d path from the satellite. Indirect signals are those which reflect off some other object before being received by the receiver. These indirect signals are known as multipath. Rejection of the indirect signals is termed multipath mitigation. When GPS receivers cannot distinguish between direct and indirect signals, position and measurement errors can occur. Receivers such as those manufactured by Ashtech are capable of using proprietary mitigation methods such as Edge Correlator(trademark) or Strobe Correlator(trademark) multipath mitigation to improve positional determination accuracy on the golf course. Antenna design can also mitigate multipath; choke rings and NovAtel""s recent Pinwheel Technology(trademark), as used in its GPS 600 antennas, are two examples of multipath mitigating antennas.
Dilution of Precision
Dilution of precision (DOP) is a measure of the receiver/satellite(s) geometry. DOP relates the statistical accuracy of the GPS measurements to the statistical accuracy of the calculated position information. Geometric Dilution of Precision (GDOP) is composed of Time Dilution of Precision (TDOP) and Position Dilution of Precision (PDOP). PDOP is composed of Horizontal Dilution of Precision (HDOP) and Vertical Dilution of Precision (VDOP). The interrelation of these elements is described by the formula GDOP2=PDOP2+TDOP2 and PDOP2=HDOP2+VDOP2. HDOP becomes an issue when a user on a golf course moves into and out of areas that are blocked from satellite reception, primarily by trees. When satellites on the horizon are blocked from view of the receiver and only satellites from more directly over head are used for the position solution, the HDOP value will increase. For example, an HDOP of 2 means that the standard deviation of the total error in a given position information waypoint will be twice the standard deviation of the GPS pseudorange error.
The data broadcasts received by GPS receivers need to be in a format recognized by the receiver for it to utilize the broadcast to determine position. Likewise, data transmitted by GPS receivers need to be in a format recognized for the receiving unit to utilize the data. Standardization of these formats facilitates wide compatibility among different forms of equipment. The following are two such standardized formats.
National Marine Electronics Association (NMEA)
NMEA has published standard formats that GPS receivers may transmit data in. An example is xe2x80x9cNMEA 0183 Standard Version 2.1xe2x80x9d. One of the data strings in the format is the GGA GPS Position Message. The format may be as follows:
$GPGGA,m1,m2,c1,m3,c2,d1,d2,f1,f2,M,f3,M,f4,d3*cc
The table below defines the format for this message:
RTCM SC-104
Another standard is the RTCM Special Committee 104 Recommended Standards for Differential Global Navigation Satellite Systems Service, Version 2.2, known as RTCMSC-104 and published in RTCM PAPER 11-98/SC104-STD. RTCM SC-104 is the standard format used for the broadcast of differential correction data by marine beacon reference stations. This is also the format accepted by GPS engines when differential correction data is passed to them via a communication port from a differential receiver.
An object of the present invention is to provide an individual player owned dGPS system that enables a golfer to positionally map and/or play a golf course whether or not the course offers positional equipment or information.
Another object of the present invention is to provide previously created maps for downloading and editing by users and to provide for the uploading of maps and play data through a public access computer system such as the Internet.
A third object of the present invention is to provide a dGPS system that would receive WAAS correction information on one of its channels. The invention will incorporate the capability to include the use of WAAS as it becomes available, thus reducing the number of receiver/antenna combinations required from two to one. This would also enable the provision of a reliably accurate locational device with lower power requirements.
A fourth object of the present invention is to provide a dGPS system capable of receiving a signal broadcast from a reference station conforming to the International Association of Maritime Aids to Navigation and Lighthouse Authorities standards. One embodiment of the differential beacon receiver implements multiple frequency reception of beacon data to allow automatic selection of the beacon signal with the best reception. Another embodiment employs a multiple channel beacon receiver using correction from 2 or more transmitters for interpolation to ameliorate atmospheric induced errors in the rover""s location.
A fifth object of the present invention is to provide a dGPS system that utilizes a FM differential receiver for the reduction of position determination errors.
A sixth object of the present invention is to provide a dGPS system that utilizes a satellite differential receiver for the reduction of position determination errors.
A seventh object of the present invention is to provide a dGPS system that utilizes multipath mitigation techniques for the reduction of position determination errors.
An eighth object of the present invention is to provide a dGPS system that utilizes differing depictions of course features corresponding to their relative HDOP, differential signal reception status, and satellite count to enable the user to evaluate the quality of the attribute mapping.
A ninth object of the present invention is to provide a dGPS system that utilizes the NMEA data message format as well as combinations of other message formats such as GLL, GSA, GSV, RMC, POS to achieve similar functionality.
A tenth object of the present invention is to provide a dGPS system in which the portable device is of modular construction to provide enhanced flexibility of utilization, increased battery life, and ease of system upgrading.
Another object of the present invention is to provide for a personal dGPS system that provides the user with complete autonomy from course owners and course owned systems with no additional reoccurring service fees or compensation for its use.
Another object of the present invention is to provide a dGPS system that is operational on golf courses that do not have on-site positioning systems.
Another object of the present invention is to provide a personal dGPS system that enables a user to transfer (upload and download) course maps over a public access computer network such as the Internet.
Another object of the present invention is to provide for a personal dGPS system that enables a player to archive, retrieve, and analyze a personal database of golf round statistics including locational data and scoring, as well as review and replay a round on a Personal Computer or at Web site. Furthermore, the invention avoids potentially incompatible play data gathered from differing course owned systems.
In one embodiment, this invention is operable without a golf cart, and carryable in one""s hand or a golf bag. It may incorporate a belt clip for constant wearing, and may be held directly over a ball lie for greatest accuracy of positioning and ball lie recording.
The present invention provides the user with the tools to personally create a horizontal vector map of any golf course as needed. The invention provides continually zoomable vector definitions (maps) of greens, fairways, hazards, boundaries, holes, cups, and other golf course attributes.
The present invention provides a heretofore absent method of golf course map creation, ongoing map modification, and map exchange between golfers worldwide via publicly accessible networks such as the Internet. It also provides a novel, on-site, dGPS mapping method and Graphical User Interface (GUI) mapping software specifically designed for easily mapping golf courses and especially effective for on site real-time editing to correct errors in a map.
One embodiment of the present invention enables the user to determine an accurate change in elevation from a current position to a practically unlimited selection of target locations.
The present invention includes a receive-only function when in operation. The elimination of the necessity of continuously sending data to another system via Radio Frequency (RF) vastly reduces power demands.
A further benefit of the present invention over a course owner controlled dGPS device is the availability of the dGPS module to the user for applications other than golf. For example, it may be used in a vehicle with a different set of software suited for vehicle navigation. With appropriate software, hikers, hunters, bikers, or farmer can benefit from its capabilities. Utility Companies may use it for locating structures. The flexibility of the present invention""s modular system enables the use of modules suitable for diverse applications.